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Abstract:

An copper alloy material for electric/electronic components containing
Co by 0.2 to 2 mass % and Si by 0.05 to 0.5 mass % and having a remaining
component composed of Cu and unavoidable impurities,characterized in that
its grain size is 3 to 35 μm and size of precipitate containing the
both of Co and Si is 5 to 50 nm, electric conductivity is 50% IACS or
more, tensile strength is 500 MPa or more and bending workability (R/t)
is 2 or less.

Claims:

1. An copper alloy material for electric/electronic components containing
Co by 0.2 to 2 mass % and Si by 0.05 to 0.5 mass % and having a remaining
component composed of Cu and unavoidable impurities,characterized in that
its grain size is 3 to 35 μm and size of precipitate containing the
both of Co and Si is 5 to 50 nm.

2. The copper alloy material for electric/electronic components as
described in claim 1, characterized in that the alloy material further
contains 0.01 to 0.5 mass % of one or two or more types selected from a
group of Fe, Ni, Cr and P.

3. The copper alloy material for electric/electronic components as
described in claim 1, characterized in that the alloy material further
contains 0.01 to 0.5 mass % of one or two or more types selected from a
group of Sn, Zn, Mg and Mn.

4. The copper alloy material for electric/electronic components as
described in claim 2, characterized in that the alloy material further
contains 0.01 to 0.5 mass % of one or two or more types selected from a
group of Sn, Zn, Mg and Mn.

5. The copper alloy material for electric/electronic components as
described in claim 1,characterized in that electric conductivity is 50%
IACS or more, tensile strength is 500 MPa or more and bending workability
(R/t) is 2 or less.

6. A method for producing an copper alloy material for electric/electronic
components to obtain a copper alloy material whose grain size is 3 to 35
μm and whose size of precipitate containing the both of Co and Si is 5
to 50 nm, characterized in that the method comprises:a step-A of carrying
out a solution recrystallizing heat treatment of a copper alloy
containing Co by 0.2 to 2 mass % and Si by 0.05 to 0.5 mass % and having
a remaining component composed of Cu and unavoidable impurities in
temperature not less than 700.degree. C. and less than 950.degree. C.;
anda step-B of carrying out a cooling process, after the previous step-A,
with an average cooling speed of 50.degree. C./sec or more from the
temperature during the solution recrystallizing heat treatment to
300.degree. C.

7. The copper alloy material for electric/electronic components as
described in claim 2,characterized in that electric conductivity is 50%
IACS or more, tensile strength is 500 MPa or more and bending workability
(R/t) is 2 or less.

8. The copper alloy material for electric/electronic components as
described in claim 3,characterized in that electric conductivity is 50%
IACS or more, tensile strength is 500 MPa or more and bending workability
(R/t) is 2 or less.

9. The copper alloy material for electric/electronic components as
described in claim 4,characterized in that electric conductivity is 50%
IACS or more, tensile strength is 500 MPa or more and bending workability
(R/t) is 2 or less.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a copper alloy material, and a
method for manufacturing the same, applied to electric/electronic
components such as a connector, a terminal material and the like of
electric/electronic apparatus or more specifically to a high-frequency
relay and a switch desired to have high conductivity or to a connector, a
terminal material, a lead frame and the like mounted in cars.

used for connectors, terminals, relays, switches and others of
electric/electronic apparatus.

[0003]Lately, frequency of electric current used in the
electric/electronic apparatus using those parts is increased and
substantial electric conductivity drops due to a skin effect, so that
materials are also required to have a high conductivity. While the
electric conductivity of brass and phosphor bronze are low from the
beginning and Corson copper alloy shows medium conductivity (EC nearly
equal 40 to 50% IACS) as a connecter member, higher conductivity is
required. Although beryllium copper has the medium conductivity, it is
expensive. Still more, because beryllium is an environmental burdening
material, it is known to be considered to replace to other copper alloy
and the like. Meanwhile, pure copper (C1100), tinned copper (C14410) and
the like, which have high conductivity, have a drawback that their
strength is low. Then, it is desired to have a copper alloy having
conductivity exceeding the prior art Corson copper, equivalent tensile
strength and bending workability.

[0004]The numbers in parentheses (CXXXX) denote types of copper alloys
specified by the JIS, and % IACS is an abbreviation of the International
Annealed Copper Standard and is unit indicating copper alloy of
materials.

[0005]In general, conductivity and strength are conflicting properties.
While there are various methods for strengthening such as solid-solution
strengthening, processing strengthening, precipitation strengthening and
the like, it is known that among them, the precipitation strengthening is
a promising method for enhancing the strength of the copper alloy without
deteriorating the copper alloy. This precipitate strengthening is a
method of treating an alloy into which element causing precipitation is
doped at high temperature to solid-solution such element in the copper
mother phase and of then treating at temperature lower than such
temperature to precipitate the solid-solution element. This strengthening
method is adopted for beryllium copper, Corson alloy and others for
example.

[0006]By the way, there are known alloys containing intermetallic
compounds of cobalt (Co) and silicon (Si) within copper, besides
beryllium copper, Corson alloy and others described above. In the
technology of the copper base alloy, using the intermetallic compound of
Co and Si, there is some conventional example.

[0007]Their known examples include a copper alloy containing Co, Si, Zn,
Mg and S as essential components (see Patent Document 1 for example) and
an alloy containing Co, Si, Mg, Sn and Zn (see Patent Document 2 for
example), a copper alloy essentially containing Co, Si, Sn and Zn (see
Patent Document 3 for example). Patent Documents 2 and 3 describe as
Co2Si compound as for the precipitate of Co and Si. There is a
document that describes a Cu--Co--Si group alloy as a copper alloy for
the use of a lead frame (see Patent Document 4 for example).

[0012]By the way, Patent Document 1 aims at improving hot workability,
describes nothing about the precipitate of Co and Si and naturally
describes nothing about how to control its size and others. Still more,
it describes no evaluation results of its strength and copper alloy in
the embodiment. Further, types of alloys are different because S is
essential.

[0013]Although Patent Document 2 describes about the precipitate of Co and
Si as the Co2Si compound, it describes nothing about its size and
its control method and leaves them unknown. Patent Document 2 carries out
only annealing of one hour at 500° C. or 450° C. and
carries out no recrystallization treatment. That is, because it is a
forced rolled material, its grain size is unclear.

[0014]Although Patent Document 3 describes about the precipitate of Co and
Si as the Co2Si compound similarly to Patent Document 2, its size
and its control method are unknown in the same manner with Patent
Document 2 and it carries out annealing for one hour at 400 to
500° C. Still more, Patent Document 3 carries out a solution
treatment at 950° C. and cold rolling before the annealing.
Because Patent Document 3 describes a high additive amount of Sn of 1
mass %, it shows a relatively low copper alloy of 30% IACS or less in its
embodiment.

[0015]While Patent Document 4 describes a copper alloy for the use of a
lead frame and describes as a precipitate strengthening type alloy, it
does not disclose its specific compound or its size. Patent Document 4
also carries out a heat treatment of one hour at 500° C. and then
only cold rolling and stress relieving annealing of one hour at
300° C. and carries out no recrystallizing treatment. Therefore,
the grain size is assumed to be unclear.

[0016]It is an ordinary case for a material applied to connectors, relays,
switches and others involving a bending work that if it is highly worked
after a recrystallizing treatment in its fabrication process, its bending
workability deteriorates due to an influence of working strain. While a
recrstallizing heat treatment must be carried out in high temperature, no
high temperature heat treatment process that cause recrystallization is
added at all after the hot rolling in the embodiments of the Patent
Documents 1, 2 and 4, so that it is judged that bending workability of
the forced rolled material is inferior.

[0017]Meanwhile, it is also known that the bending workability is inferior
if grain size is coarse in composition of an alloy. However, solution
temperature of Patent Document 3 is so high as 950° C. and the
higher the temperature, the coarser the grain size is, so that it is
judged that the bending workability of this material is also inferior.
Still more, 950° C. is close to a fusion point of copper alloy, so
that the shape of the material is not stabilized. Still more, because a
special material has to be used for a fire-resistant material of a
furnace of the heat treatment when the temperature is high, it is
disadvantageous condition industrially.

Means for Solving the Problems

[0018]Thus, it was found that it is unable to obtain a desirable material
just by the known technologies as disclosed in the respective Patent
Documents described above to develop a copper alloy having a high
conductivity, high strength and favorable bending workability. Still
more, it was found that it is important to adequately control grain size
in order to obtain a material having the favorable bending workability.

[0019]Then, in view of the problems described above, the present invention
aims at providing a copper alloy material, and its fabrication method,
that excels in the three points of the high copper alloy, high strength
and bending workability and suitable for electric/electronic components
such as connectors, terminal materials, relays and others.

[0020]The inventor et al. studied a copper alloy suitable for the use of
the electric/electronic components and found that it is important to meet
characteristics of 50% IACS or more of conductivity, 500 MPa or more of
tensile strength and R/t≦2 of bending workability in the same
time.

[0021]Here, R in R/t is a bending radius and t is a plate thickness. It
indicates that the lower the value, the better the bending workability
is.

[0022]Then, in order to achieve the high conductivity, high strength and
favorable bending workability, the inventor et al. obtained specific
component compositions, defined grain size, found the optimum
relationship with size of precipitate and consummated the invention by
reviewing the study.

[0023]The invention provides the following means:

[0024](1) An copper alloy material for electric/electronic components
containing Co by 0.2 to 2 mass % and Si by 0.05 to 0.5 mass % and having
a remaining component composed of Cu and unavoidable impurities,

[0025]characterized in that its grain size is 3 to 35 μm and size of
precipitate containing the both of Co and Si is 5 to 50 nm.

[0026](2) The copper alloy material for electric/electronic components as
described in the aspect (1), characterized in that the alloy material
further contains 0.01 to 0.5 mass % of one or two or more types selected
from a group of Fe, Ni, Cr and P.

[0027](3) The copper alloy material for electric/electronic components as
described in the aspect (1), characterized in that the alloy material
further contains 0.01 to 0.5 mass % of one or two or more types selected
from a group of Sn, Zn, Mg and Mn.

[0028](4) The copper alloy material for electric/electronic components as
described in the aspect (2), characterized in that the alloy material
further contains 0.01 to 0.5 mass % of one or two or more types selected
from a group of Sn, Zn, Mg and Mn.

[0029](5) The copper alloy material for electric/electronic components as
described in any one of the aspects (1) through (4), characterized in
that electric conductivity is 50% IACS or more, tensile strength is 500
MPa or more and bending workability (R/t) is 2 or less.

[0030](6) A method for manufacturing an copper alloy material for
electric/electronic components to obtain a copper alloy material whose
grain size is 3 to 35 μm and whose size of precipitate containing the
both of Co and Si is 5 to 50 nm, characterized in that the method
comprises:

[0031]a step-A of carrying out a solution recrystallizing heat treatment
of a copper alloy containing Co by 0.2 to 2 mass % and Si by 0.05 to 0.5
mass % and having a remaining component composed of Cu and unavoidable
impurities in temperature not less than 700° C. and less than
950° C.; and

[0032]a step-B of carrying out a cooling process, after the previous
step-A, with an average cooling speed of 50° C./sec or more from
the temperature during the solution recrystallizing heat treatment to
300° C.

[0033]It is noted that the "high conductivity" here means that electric
conductivity is 50% IACS or more.

ADVANTAGEOUS EFFECTS OF THE INVENTION

[0034]The invention permits to obtain the copper alloy material that has
the three characteristics of the high copper alloy, high strength and
excellent bending workability and is suitable for parts of the
electric/electronic apparatus by limiting the grain size and controlling
the minute size of the precipitate of the alloy having the specific
composition of Cu--Co--Si. Still more, the copper alloy material having
the more excellent characteristics may be obtained by adding Fe, Ni, Cr
and P as well as Sn, Zn, Mg and Mn as alloy components.

[0035]Still more, it is possible to control the grain size and the size of
the precipitate and to obtain the copper alloy material having the
excellent characteristics by carrying out the solution recrystallizing
heat treatment in specific temperature and by limiting its cooling speed.

[0036]The above and other features and advantages of the invention will be
more apparent from the description below by appropriately making
reference to the appended drawing.

BRIEF DESCRIPTION OF DRAWING

[0037]FIG. 1 is a graph showing one exemplary cooling speed of various
cooling solutions.

BEST MODE FOR CARRYING OUT THE INVENTION

[0038]A preferable mode of an alloy composition of a copper alloy material
of the present invention will be explained in detail below. It is noted
that the copper alloy material of the invention is a copper alloy
material having a specific shape such as a plate, strip, wire, rod, foil
and the like and may be used for any kinds of electric/electronic
components. Although the parts are not specifically limited, the copper
alloy material may be suitably used for connector, terminal materials and
the like, high-frequency relays and switches desired to high conductivity
in particular, or connectors, terminal materials and lead frames mounted
in cars.

[0039]Co and Si are essential components in the composition of the copper
alloy of the invention. Co and Si within the copper alloy mainly form the
precipitate of Co2Si intermetallic compound to improve strength and
electric conductivity.

[0040]An amount of Co is 0.2 to 2 mass %, or preferable to be 0.5 to 1.5
mass % or more preferable to be 0.8 to 1.4 mass %. An amount of Si is
0.05 to 0.5 mass %, or preferable to be 0.1 to 0.45 mass % or more
preferable to be 0.18 to 0.35 mass %. The reason why their amounts are
specified as such is because they form the precipitate of intermetallic
compound of Co2Si and contribute for precipitate strengthening. If
the amount of Co is too little, the precipitate strengthening amount is
small and the amount is excessive, its effect is saturated. Further,
while the optimum additive ratio from stoichiometric proportion of
compounds is Co/Si≈4.2, it is preferable to modify Co/Si so that
the value falls within a range from 3.0 to 6.0 or more preferable to be
3.8 to 4.6 centering on that value described above.

[0041]Further, there is a preferable range in a relationship between the
additive amount of Co and the temperature at which the solution
recrystallizing heat treatment is carried out. For instance, when the
additive amount of Co is 0.2 to 0.8 mass %, the temperature at which the
solution recrystallizing heat treatment is carried out is preferable to
be in a range of 700 to 800° C., when the additive amount of Co is
0.5 to 1.2 mass %, the temperature at which the solution recrystallizing
heat treatment is carried out is preferable to be in a range of 800 to
900° C. and when the additive amount of Co is 1.0 to 2.0 mass %,
the temperature at which the solution recrystallizing heat treatment is
carried out is preferable to be in a range of 900 to 950° C. The
temperature at which the solution recrystallizing heat treatment is
carried out is not limited to the abovementioned temperature ranges as a
matter of course, the abovementioned temperature ranges are desirable
ranges based on the grain size described later.

[0042]It is also preferable to add either one or two or more types of Fe,
Ni, Cr and P to the copper alloy of the invention and its amount is 0.01
to 0.5 mass % or preferably 0.2 to 0.4 mass %. These elements function to
improve the strength by replacing with part of main precipitated phase of
Co and forming the (Co, λ)2Si compound (λ=Fe, Ni, Cr, P)
(`The precipitate containing the both of Co and Si` includes `precipitate
containing Co and Si as well as one or two or more elements among Fe, Ni,
Cr and P` besides `precipitate containing Co and Si`). If the additive
amount is too little, the effect of the addition is small and if it is
too much in contrary, the element(s) hampers the conductivity by
solid-solutioning into the copper mother phase and forming other
compounds (noncoherent precipitate) having no strengthening action.

[0043]Still more, it is preferable to add either one or two or more types
of Sn, Zn, Mg and Mn to the copper alloy of the invention and its amount
is 0.01 to 0.5 mass % or preferably 0.08 to 0.3 mass %. These elements
have an action of strengthening the copper alloy by solid-solutioning to
the copper mother phase. Due to that, they are not effective if their
amount is too little and they hamper the conductivity if their amount is
too much. Therefore, it is preferable to keep them in this amount. It is
noted that Zn has an effect of improving soldering adhesion and Mg and Mn
has an effect of hot workability.

[0044]Fe, Ni, Cr and P and Sn, Zn, Mg and Mn will not hamper the
respective characteristics even if they are added in complex if their
amount is within the limited range.

[0045]The invention specifies the grain size and the size of the
precipitate containing the both of Co and Si strictly to suitably realize
the characteristics of the copper alloy material composed as described
above. In the invention, the grain size is 3 to 35 μm or preferably 5
to 20 μm. The reason for that is because if the grain size is too
small, duplex grain size containing parts fully recrystallized and
unrecrystallized parts not fully recrystallized is prone to be generated
and bending workability drops. If the grain size is too large on the
other hand, grain boundary density is low because the grain diameter is
coarse, so that it is assumed that the workability drops because it is
unable to fully absorb bending stress. It is noted that the `grain size`
is a value measured based on the JIS-H0501 (cutting method) described
later.

[0046]Still more, the size of the precipitate of the compound mainly
containing the both of Co and Si is set to be 5 to 50 nm in the copper
alloy material of the invention. This compound enhances by precipitating
coherently with the copper mother phase. The size is limited in this
range because it is unable to obtain an enough precipitate strengthening
amount if the size is too small and it loses the coherence and drops the
strength in contrary if the size is too large. The desirable size of the
precipitate is 10 to 30 nm.

[0047]The `size of the precipitate` here is an average size of the
precipitate found by a method described later.

[0048]The copper alloy material for electric/electronic components of the
invention is preferable to have characteristics of 50% IACS or more of
electric conductivity, 500 MPa or more of tensile strength and 2 or less
of bending workability (R/t). The reason of that is based on the
necessity of meeting with the required minimum conductivity, tensile
strength and bending workability for electric/electronic components
demanded by the market in pursuit of downsized and high-performance
electric/electronic apparatus. The more preferable electric conductivity
is 55% IACS or more or more preferable to be 60% IACS or more. Even
though it is preferable to be higher, its upper limit is normally around
70% IACS. The more preferable tensile strength is 550 MPa or more or more
preferable to be 600 MPa or more. Even though it is preferable to be
higher, its upper limit is normally around 850 MPa. The more preferable
bending workability (R/t) is 1.5 or less or more preferable to be 1 or
less. Even though it is preferable to be smaller, its lower limit is zero
practically.

[0049]Next, a preferable method for producing the copper alloy material of
the invention is implemented in the following mode. An outline of the
main fabrication process of the copper alloy material of the invention is
dissolution, casting, hot rolling, facing, cold rolling, solution
recrystallizing heat treatment, rapid quenching, aging heat treatment,
final cold rolling and low-temperature annealing. The order of the aging
heat treatment and the final cold rolling may be reversed. The final
low-temperature annealing may be also cut.

[0050]In the invention, it is preferable to carry out the solution
recrystallizing heat treatment before the final cold rolling in a range
not less than 700° C. and less than 950° C. The reason why
the temperature range is thus specified is because it is necessary to be
700° C. or more to fully solution-treat and recrystallize the
element such as Co described above. The temperature is not also
preferable industrially to be 950° C. or more because it is close
to the fusion of copper and causes such problems that the material may
partially melt and the shape may be deformed. The solution treatment and
the recrystallizing treatment may be fully carried out and the
fabrication may be stably carried out industrially if the temperature is
more than 800° C. and less than 950° C. The grain size in
the copper alloy material is decided by the recrystallization solution
heat-treatment of this temperature.

[0051]Further, the rapid quenching of 50° C./sec or more of cooling
speed from the solution recrystallizing heat treatment temperature is
preferable in the invention. If the rapid quenching is not achieved, the
solution-treated element in the high temperature described above may
precipitate. The particles (compound) precipitated during this cooling is
noncoherent precipitate not contributing to the strength and may give an
adverse effect to the characteristics by contributing as a nucleus
generating site in forming coherent precipitate in the next aging heat
treatment step and by promoting precipitation of that part.

[0052]The cooling speed is preferable to be 80° C./sec or more and
more preferable to be 100° C./sec or more. Even though faster
quenching speed is desirable, its practical upper limit is normally
200° C./sec.

[0053]It is noted that this cooling speed means an average speed from the
solution recrystallizing heat treatment temperature to 300° C.
Because no large change of structure occurs in the temperature under
300° C., it is just necessary to appropriately control the cooling
speed to this temperature.

[0054]It is preferable to carry out the aging heat treatment after the
solution recrystallizing heat treatment or after the final cold rolling
after that in the invention. Preferably, the aging heat treatment is
carried out from 450° C. to 600° C. or more preferably from
500° C. to 575° C. It is also preferable to carry out the
aging heat treatment for one to four hours or more preferably for two to
three hours.

[0055]It is more preferable to carry out the aging heat treatment from
525° C. to 575° C. in carrying out the aging heat treatment
before the final cold rolling.

[0056]It is preferable to carry out the aging heat treatment from
450° C. to 575° C. or more preferably from 475° C.
to 525° C. in carrying out the aging heat treatment after the
final cold rolling. It is because a precipitation temperature zone shifts
to the low-temperature side by the cold rolling process.

[0057]A processing rate in the final cold rolling (i.e.,
(H-H1)/H×100: where H denotes a plate thickness before the
final cold rolling and H1 denotes a plate thickness after the final
cold rolling) is preferable to be 5 to 25% or more preferable to e 5 to
10%.

[0058]Although the low-temperature annealing (strain relieving annealing)
may be carried out by the ordinary method, it is preferable to carry out
from 300° C. to 450° C. or more preferably from 350°
C. to 400° C. and for 5 to 120 seconds or more preferably for 10
to 30 seconds.

EMBODIMENTS

[0059]Next, while the invention will be explained in more detail based on
embodiments thereof, the invention is not limited to them.

First Embodiment

[0060]The copper alloy used in the embodiment of the invention and in
comparative examples are alloys containing the components shown in Tables
1 and 2 and having the remaining parts composed of Cu and the unavoidable
impurities (Examples of the invention Nos. 1 through 30) and comparative
examples Nos. 1 through 20). The respective alloys are melted in a
high-frequency melting furnace and are casted with 10 to 30°
C./sec of cooling speed to obtain ingot of 30 mm thick, 100 mm width and
150 mm long.

[0061]The ingot thus obtained was held for 0.5 to 1.0 hour in 930°
C. to 970° C. After that, hot rolling was carried out to fabricate
a hot rolled plate having a thickness t=12 mm. The both faces thereof
were faced by 1 mm each so as to be t=10 mm. Next, it is finished to be
t=0.3 mm by cold rolling and the solution recrystallizing heat treatment
was carried out in temperature from 700° C. to 950° C. The
final copper alloy material was prepared by implementing either one of
the following two steps on the material treated by the solution
recrystallizing heat treatment

[0063]It is noted that the strain relieving annealing was implemented for
one to two hours in temperature of 300 to 400° C. after the final
cold rolling to relieve the strain caused by the final cold rolling.

[0065]Tables 1 and 2 show the solution recrystallizing heat treatment
temperatures, the cooling speeds in rapid quenching process, aging heat
treatment temperatures, aging heat treatment times, processing rates of
the final cold rolling adopted in the examples of the invention and in
the comparative examples.

[0066]The following characteristic investigation was carried out on the
samples of the final copper alloy material and their results were shown
Table 1 (examples of the invention) and Table 2 (comparative examples).

[0067]a. Grain Size:

[0068]The grain size was measured according to the cutting method in the
JIS H0501 by mirror-finishing a section of the sample perpendicular to
the rolling direction of the test piece by wet polishing and buffing, by
fretting the polished surface for several seconds by a solution of
chromic acid:water=1:1 and by photographing by an optical microscope at
200 to 400-fold magnification or at 500 to 2000-fold magnification by
using a secondary electronic image of a scanning electronic microscope
(SEM).

[0069]It is noted that the "duplex grain" in Table means a structure in
which the both of recrystallized grains and nonrecrystallized grains
(residue of rolling) are mixed and the grain size was not measured in the
case of the duplex grain size. It is said that bending workability is
deteriorated if nonrecystallized grains exist. Therefore, the duplex
grain size is an undesirable structure.

[0070]b. Size of Precipitate:

[0071]The size of the precipitate was evaluated by using a transmission
electron microscope. Because it becomes difficult to observe the final
copper alloy material due to an influence of processing strain (in the
case of the step-A in particular), the structure of the material after
the aging heat treatment was observed. It is because the size and density
of the precipitate do not change by the strain relieving annealing and
the cold rolling and the size of the precipitate after the aging heat
treatment coincides with the size of the precipitate of the final copper
alloy material. A test piece for observation was completed by cutting out
a test piece for the TEM from an arbitrary part of the material treated
by the aging heat treatment and by carrying out electrolytic polishing
(Twin Jet: manufactured by Storas Co.) by a methanol solution of nitric
acid (20%) in temperature from -20° C. to -25° C.

[0072]After that, observation was carried out with 300 kV of acceleration
voltage, incidence azimuth of an electron beam was adjusted to the
vicinity of (001) and three pictures of 100.000-fold magnification were
taken arbitrarily. The average size of the precipitate (about 100 pieces)
was found by using those pictures.

[0073]c. Tensile Strength:

[0074]Tensile strength of three test pieces of JIS Z2201-13B cut out in
the rolling parallel direction of the respective samples was measured
under conditions of 10 mm/min. of tensile speed and 50 mm of gauge length
based on JIS Z2241 and their average value was found.

[0075]d. Measurement of Electrical Conductivity:

[0076]The electric conductivity was measured for two test pieces of the
respective samples within a constant-temperature bath controlled at
20° C. (±1° C. by using a four-terminal method and their
average value (% IACS) was found. A distance between the terminals was
100 mm.

[0077]e. Bending Workability:

[0078]The respective samples were cut perpendicularly in the rolling
direction to be 10 mm in width and 35 mm long. They are then bent by
90° W bending (Bad-way bending) so that an axis of bending is
paralleled with the rolling direction. It was then investigated whether
or not any crack exists in the bent part by observing visually with
50-fold magnification by the optical microscope and by the scanning
electron microscope (SEM). Eight levels of bending radius R were set (R=0
to 0.5 mm: i.e., 0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4 and 0.5 mm).

[0079]It is noted that the evaluation result was represented by R/t (R:
bending radius, t: plate thickness) and R/t was calculated by adopting R
at the limit causing a crack. If no crack is generated when R=0.15 (mm)
and a crack is generated when R=1 (mm) and when the thickness (t)=0.15
mm, it was represented as R/t=0.15/0.15=1.

[0080]In the embodiment, the adjustment of the cooling speed was carried
out by changing the type and amount of the cooling solution in the bath
for implementing quenching. Three cooling solutions of water (water
temperature: 20 to 30° C.), silicone oil (liquid temperature: 20
to 30° C.) and salt bath (liquid temperature: 300° C.,
nitrate salt was used) were prepared. It is noted that in the case of the
salt bath, water bath was also used for cooling (secondary cooling) less
than 300° C. to cool down to the normal temperature. FIG. 1 shows
one exemplary cooling speed of the various cooling solutions. This data
shows a result measured by attaching a thermocouple to the test pieces
(50×150×0.2 mm).

[0081]An amount of all of the cooling solutions in this case was about
five liters and the cooling speed was fast in an order of
water>silicone oil>salt bath. It is noted that when the test was
also carried out by changing the condition of the cooling solutions from
the test described above, while the curve of the cooling speed became
moderate when the amount of the cooling solution was reduced, the cooling
speed was not improved remarkably even if the amount of the cooling
solution was increased.

[0082]All of the copper alloy materials of Nos. 1 through 30 of the
examples of the invention show high strength, high conductivity and
favorable bending workability.

[0083]In contrary to that, Nos. 1 through 13 of the comparative examples
include ones out of the range of the mode described above in the aspect
(1) and do not satisfy at least one of the strength, conductivity and
bending workability. Further, Nos. 11 through 15 are comparative examples
related to the mode described above in the aspect (2) and are out of the
range of the composition specified in the aspect (2) and Nos. 16 through
18 are comparative examples related to the mode described above in the
aspect (3), are out of the range of the composition specified in the
aspect (3) and do not satisfy at least one of the strength, conductivity
and bending workability.

[0084]Then, Nos. 19 and 20 are comparative examples related to the mode
descried above in the aspect (5) and are out of the range of the mode
specified in the aspect (5), so that they are inclined to be inferior in
terms of tensile strength and bending workability as compared to the
examples 1 through 4 of the invention (the examples 2 and 3 of the
invention in particular) that are within the range of the mode described
in the aspect (5).

[0085]While the invention has been explained with the embodiment thereof,
the invention should not be limited to any detail of the explanation
unless specially specified and should be construed widely without
departing the spirit and scope of the invention specified in the appended
claims.

[0086]This application claims the foreign priority benefit under Japanese
Patent Application No. 2008-022088, filed on Jan. 31, 2008 in the Japan
Patent Office, the disclosure of which is herein incorporated by
reference in its entirety.